Re: the " 'official' point of view" expressed by kernelnewbies.org regarding reiser4 inclusion

Edward Shishkin
2006-08-04T17:04:42Z

Hans Reiser wrote:
> Edward Shishkin wrote:
>
>
>>Matthias Andree wrote:
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>>>On Tue, 01 Aug 2006, Hans Reiser wrote:
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>>>
>>>>You will want to try our compression plugin, it has an ecc for every
>>>>64k....
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>>>
>>>
>>>What kind of forward error correction would that be,
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>>Actually we use checksums, not ECC. If checksum is wrong, then run
>>fsck - it will remove the whole disk cluster, that represent 64K of
>>data.
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> How about we switch to ecc, which would help with bit rot not sector loss?

Interesting aspect.

Yes, we can implement ECC as a special crypto transform that inflates
data. As I mentioned earlier, it is possible via translation of key
offsets with scale factor > 1.

Of course, it is better then nothing, but anyway meta-data remains
ecc-unprotected, and, hence, robustness is not increased..

Edward.

>
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>> and how much and
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>>>what failure patterns can it correct? URL suffices.
>>>
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>>Checksum is checked before unsafe decompression (when trying to
>>decompress incorrect data can lead to fatal things). It can be
>>broken because of many reasons. The main one is tree corruption
>>(for example, when disk cluster became incomplete - ECC can not
>>help here). Perhaps such checksumming is also useful for other
>>things, I didnt classify the patterns..
>>
>>Edward.
>>
>>
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